The disclosed technology relates to an improved method for evaluating the effect of soot on lubricant oils, on a bench scale test.
Modern heavy diesel (HD) engine oils must have sufficient dispersancy to keep soot (a product of the incomplete combustion of diesel fuel) suspended in the bulk oil. Various API engine oil categories require minimum soot dispersion performance as measured by fired engine tests. For example, API CH-4 and CI-4 oils must exhibit good soot dispersion in the Mack T8E engine test. Such fired engine tests are lengthy and expensive. For instance, modern HD engine oil soot dispersion tests such as the Mack T8E and Mack T11 require as long as 2 weeks to complete and cost as much as 80,000 USD. A formulator may need to screen dozens of formulas in order to find one with acceptable performance.
An efficient, easy, and short screening method for predicting the performance of oils in sooted engine tests is highly desirable. Such a screen test is described herein. The current invention gives the HD formulator a tool to perform such screening in an efficient and inexpensive manner. The new test described here has better predictive ability and is more visually impactful than earlier soot screen tests. The new inventive screen test correctly predicts engine test performance of API CH-4 oils while older screen tests do not. The screen test described here is a blotter strip test and is an improvement on earlier blotter spot tests as described, for instance, in WO2010/099136, Sep. 2, 2010, Gieselman et al.; see for instance paragraph 0137.
Older soot dispersion tests are sometimes run in the blotter spot mode. While the test is appropriate for showing the difference in performance between very poor oil and top tier oils, it is not appropriate for distinguishing between oils with finer differences in performance. Another advantage of the disclosed test is that it can distinguish in a statistically significant way between fair performing oils and good performing oils.